• Korea Trade Review
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• v.47 no.3
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• pp.211-232
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• 2022

Due to the impact of the public health event COVID-19 epidemic, the Chinese futures market showed "Black Swan". This has brought the unpredictable into the economic environment with many commodities falling by the daily limit, while gold performed well and closed in the sunshine(Yan-Li and Rui Qian-Wang, 2020). Volatility is integral part of financial market. As an emerging market and a special precious metal, it is important to forecast return of gold futures price. This study selected data of the SHFE gold futures returns and conducted an empirical analysis based on the generalised autoregressive conditional heteroskedasticity (GARCH)-type model. Comparing the statistics of AIC, SC and H-QC, ARMA (12,9) model was selected as the best model. But serial correlation in the squared returns suggests conditional heteroskedasticity. Next part we established the autoregressive moving average ARMA-GARCH-type model to analysis whether Volatility Clustering and the leverage effect exist in the Chinese gold futures market. we consider three different distributions of innovation to explain fat-tailed features of financial returns. Additionally, the error degree and prediction results of different models were evaluated in terms of mean squared error (MSE), mean absolute error (MAE), Theil inequality coefficient(TIC) and root mean-squared error (RMSE). The results show that the ARMA(12,9)-TGARCH(2,2) model under Student's t-distribution outperforms other models when predicting the Chinese gold futures return series.

• International journal of advanced smart convergence
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• v.12 no.4
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• pp.407-417
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• 2023

The purpose of this study is to identify the level of safety perception, ethical awareness, and safety activities of nursing students for patients, and to identify the correlation and impact between them. The research design is a descriptive survey study, and the subject of the study were 197 nursing college students in G City. Safety perception, ethical awareness, and safety activity tools were used for, and the data collection period was from October 17 to 28 in 2022. T-test, one-way ANOVA, Pearson's correlation coefficient, Regression analysis were used to analyze data. The result of the study indicated that the average level of safety perception of nursing students was 3.72 points, the average ethical awareness of patients, professional work, and cooperators perceived by nursing students was 3.04 points, and the safety activities of nursing students were 4.20 points. In the case of safety awareness and ethics awareness, r=.327, a significant positive correlation, in the case of safety awareness and safety activities, r=.399, significant positive correlation, ethics awareness and safety activities as r=.296. And so on these results showed that high safety perception increases safety activities, and high ethical awareness increases safety activities. Therefore, we need practical and step-by-step convergence education to equip nursing students with patient safety nursing capabilities. To this end, a safer environment will be created if the social support network for the systematic application of safety education is well formed.

• Journal of Ocean Engineering and Technology
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• v.38 no.1
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• pp.1-9
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• 2024

The vertical center of gravity (VCG) has a significant impact on the roll motion response of a surface ship, particularly oil tankers based on the oil level in the tanker after discharging oil at several stations or positional changes, such as changes in the superstructure and deck structure. This study examined the motion response of the Korea very large crude carrier 2 (KVLCC2) at various VCGs, especially roll motion when the VCG changed. The potential theory in the Ansys AQWA program was used as a numerical simulation method to calculate the motion response. On the other hand, the calculations obtained through potential theory overestimated the roll amplitudes during resonance and lacked precision. Therefore, roll damping is a necessary parameter that accounts for the viscosity effect by performing an experimental roll decay. The roll decay test estimated the roll damping coefficients for various VCGs using Froude's method. The motion response of the ship in regular waves was evaluated for various VCGs using the estimated roll-damping coefficients. In addition, the reliability of the numerical simulation in motion response was verified with those of the experiment method reported elsewhere. The simulation results showed that the responses of the surge, sway, heave, pitch, and yaw motion were not affected by changing the VCG, but the natural frequency and magnitude of the peak value of the roll motion response varied with the VCG.

• Geomechanics and Engineering
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• v.37 no.3
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• pp.197-211
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• 2024

This research studies the effect of geotechnical factors on EPB-TBM performance parameters. The modeling was performed using simple and multivariate linear regression methods, artificial neural networks (ANNs), and Sugeno fuzzy logic (SFL) algorithm. In ANN, 80% of the data were randomly allocated to training and 20% to network testing. Meanwhile, in the SFL algorithm, 75% of the data were used for training and 25% for testing. The coefficient of determination (R²) obtained between the observed and estimated values in this model for the thrust force and cutterhead torque was 0.19 and 0.52, respectively. The results showed that the SFL outperformed the other models in predicting the target parameters. In this method, the R² obtained between observed and predicted values for thrust force and cutterhead torque is 0.73 and 0.63, respectively. The sensitivity analysis results show that the internal friction angle (φ) and standard penetration number (SPT) have the greatest impact on thrust force. Also, earth pressure and overburden thickness have the highest effect on cutterhead torque.

• Steel and Composite Structures
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• v.50 no.2
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• pp.149-158
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• 2024

Considering that different boundary conditions can have an important impact on structural vibration characteristics. In this paper, the nonlinear forced vibration behavior of functionally graded material (FGM) doubly curved shells with initial geometric imperfections under different boundary conditions is studied. Considering initial geometric imperfections and von Karman geometric nonlinearity, the nonlinear governing equations of FGM doubly curved shells are derived using Reissner's first order shear deformation (FOSD) theory. Three different boundary conditions of four edges simply supported (SSSS), four edges clamped (CCCC), clamped-clamped-simply-simply (CCSS) were studied, and a system of nonlinear ordinary differential equations was obtained with the help of Galerkin principle. The nonlinear forced vibration response of the FGM doubly curved shell is obtained by using the modified Lindstedt Poincare (MLP) method. The accuracy of this method was verified by comparing it with published literature. Finally, the effects of curvature ratio, power law index, void coefficient, prestress, and initial geometric imperfections on the resonance of FGM doubly curved shells under different boundary conditions are fully discussed. The relevant research results can provide certain guidance for the design and application of doubly curved shell.

• Journal of Korean society of Dental Hygiene
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• v.23 no.6
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• pp.493-499
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• 2023

Objectives: This study sought to identify dental hygiene students' adult attachment, interpersonal competence, self-respect, and sociable support, and to identify factors that affect interpersonal competence. Method: A self-administered survey was conducted on 180 students attending dental hygiene schools nationwide from 14 February to 30 May, 2023. Descriptive statistics, t-test, one-way ANOVAs, Pearson correlation coefficient, and stepwise multiple linear regression analys were used, as determined by the SPSS 26.0 program. Results: Dental hygiene students' interpersonal competence measured 3.61 points, adult attachment measured 3.44 points, self-respect measured 3.44 points, and sociable support measured 4.00 points. In terms of general characteristics, significant differences were found in satisfaction with college life and club membership. Interpersonal competence was positively correlated with adult attachment, self-respect, and sociable support. The factor that had the greatest impact on interpersonal competence of dental hygiene students was sociable support, with an explanatory power of 37.3%. Conclusions: In order to improve the sociable support for dental hygiene students, a social activity support network within and outside of school is needed.

• New & Renewable Energy
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• v.20 no.1
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• pp.79-87
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• 2024

This study introduces a method for estimating Aerosol Optical Depth (AOD) using Broadband Aerosol Optical Depth (BAOD) derived from direct normal irradiance and meteorological factors observed between 2016 and 2017. Through correlation analyses between BAOD and atmospheric components such as Rayleigh scattering, water vapor, and tropospheric nitrogen dioxide, significant relationships were identified, enabling accurate AOD estimation. The methodology demonstrated high correlation coefficients and low Root Mean Square Errors (RMSE) compared to actual AOD₅₀₀ measurements, indicating that the attenuation effects of water vapor and the direct impact of tropospheric nitrogen dioxide concentration are crucial for precise aerosol optical depth estimation. The application of BAOD for estimating AOD₅₀₀ across various time scales-hourly, daily, and monthly-showed the approach's robustness in understanding aerosol distributions and their optical properties, with a high coefficient of determination (0.96) for monthly average AOD₅₀₀ estimates. This study simplifies the aerosol monitoring process and enhances the accuracy and reliability of AOD estimations, offering valuable insights into aerosol research and its implications for climate modeling and air quality assessment. The findings underscore the viability of using BAOD as a surrogate for direct AOD₅₀₀ measurements, presenting a promising avenue for more accessible and accurate aerosol monitoring practices, crucial for improving our understanding of aerosol dynamics and their environmental impacts.

• Transactions of Materials Processing
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• v.33 no.2
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• pp.112-117
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• 2024

In this study, the friction and wear characteristics of Inconel 600 in the superplastic forming process of Ti6Al4V were evaluated through pin-on-disc tests. To achieve an efficient and systematic experimental design, the Taguchi method was employed. The wear track of the Inconel 600 pin showed scratches in the sliding contact direction, confirming that the wear mechanism is abrasive wear. Through sensitivity analysis such as ANOVA and Main effects, it was confirmed that both normal force and sliding distance have a significant impact on the wear. Changes in sliding velocity and distance did not affect the friction coefficient, which remained relatively constant at approximately 0.380. The wear prediction model for Inconel 600 in the superplastic forming of Ti6Al4V was constructed, which can be utilized as a guideline for the prediction and management of tool wear.

• Journal of Korean Critical Care Nursing
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• v.17 no.2
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• pp.83-95
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• 2024

Purpose : This study aimed to investigate the impact of clinical reasoning competence, positive psychological capital, and nursing work environment on nursing performance of intensive care unit (ICU) nurses in tertiary general hospitals. Methods : Data were collected from 169 ICU nurses in tertiary general hospitals in Busan, South Korea, from July 27 to August 15, 2023, using a self-report questionnaire. After excluding 12 questionnaires with insufficient responses, 157 responses were analyzed. Descriptive statistics, independent t-test, one-way ANOVA, Pearson's correlation coefficient, and stepwise multiple regression analysis were employed. Results : Factors influencing nursing performance included clinical reasoning competence (β=.51, p <.001), hope as a subfactor of positive psychological capital (β=.31, p <.001), and the nursing foundations for quality of care in the nursing work environment (β=.21, p <.001). The explanatory power of the regression model was 62% (F=87.41, p <.001). Conclusion : The study underscores the importance of improving clinical reasoning competence among ICU nurses to enhance nursing performance and foster a hopeful attitude through reflective practices and personal growth. Organizational interventions, such as educational and psychological support programs, along with creating a supportive nursing environment, are crucial for improving nursing performance among intensive care unit nurses.

• Journal of Digital Policy
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• v.3 no.3
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• pp.1-7
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• 2024

The purpose of this study is to analyze the correlation between walking time and lifespan across individuals of various ages and weights to validate the health benefits of walking exercise. The research utilized Python and related libraries to collect and preprocess data, and then analyzed the relationship between walking time and lifespan using Pearson's correlation coefficient. The study was conducted over a period of six months. The analysis results showed a trend towards increased lifespan with longer walking times, which was similarly observed in data using vitamin B2 and folate intake as surrogate variables. These findings suggest that walking exercise may have a positive impact on health and lifespan, and can be used as foundational data for the development of personalized health management services and related policy formulation.